Most chewing gum is partly plastic. The chewy part of an ordinary stick or pellet, the bit that survives after the flavour and sweetener have gone, is usually built on synthetic polymers, the same family of materials used in glues, bottles and car tyres. Food-grade versions, permitted and regulated, but polymers all the same. The reason almost nobody knows this is that labelling rules let the whole lot be declared with two words: gum base.
What "gum base" means on a label
Turn over almost any pack of gum in Australia and the ingredient list will include the words "gum base" as if they named a single thing. They do not. Gum base is a category, and food labelling rules in Australia, the United States and the European Union all allow a manufacturer to declare the entire category collectively rather than listing what is in it.
That is the whole trick. Every other ingredient in the pack has to be named. The base, which is the part you are actually chewing for twenty minutes, is the one part that does not.
What is actually in a synthetic gum base
A modern gum base is an engineered blend. The exact recipe is a trade secret at each manufacturer, which is another reason the collective term is so convenient, but the categories of ingredient are well documented:
- Elastomers, which provide the stretch and bounce. Polyisobutylene (a form of butyl rubber), styrene-butadiene rubber and polyvinyl acetate are the common ones. Polyvinyl acetate is also the basis of ordinary white wood glue.
- Resins, natural or synthetic, which hold the elastomer together and give the chew its body.
- Plasticisers and softeners, such as waxes and vegetable oils, which keep the base from going hard.
- Fillers, typically calcium carbonate or talc, which add bulk and texture.
- Antioxidants, to stop the fats and oils in the base going rancid on the shelf.
None of this is dangerous to chew. It is not going to hurt you, and it is all approved for use in food. The point is not danger. The point is that a pack can carry a two-word placeholder where the real answer is a list of industrial polymers, and most people chewing it have no idea.
How gum became plastic: the short history
Chewing gum did not start this way. For most of its history it was tree sap.
The Maya and the Aztecs chewed chicle, the milky latex of the sapodilla tree, for centuries before Europeans arrived. In the 1870s a New York inventor named Thomas Adams, who had been trying and failing to turn chicle into a rubber substitute, gave up and sold it as chewing gum instead. Chicle gum became an industry. Before that, Americans had chewed spruce resin and paraffin wax.
Chicle stayed the standard base until the middle of the twentieth century. Then demand outgrew the supply of wild sapodilla trees, the war disrupted trade with Central America, and chemists found that synthetic polymers were cheaper, more consistent and easier to scale. By the 1950s the industry had switched. Most of it never switched back.
Why it matters
Two reasons, one practical and one about honesty.
The practical one is that synthetic gum base does not readily break down. That is why chewed gum is a fixture of pavements, why councils budget for scraping it off, and why Singapore famously banned the sale of most chewing gum in 1992. A chewed piece of polymer gum is, functionally, a small piece of discarded plastic.
The honesty one is simpler. If you read ingredient lists at all, and a growing number of people do, you are entitled to know what you are putting in your mouth. "Gum base" is a legal way of not telling you.
What a tree-sap base is
The alternative is the original one. A small number of gum makers still build their base from plant saps rather than synthetic polymers. The two that matter most are:
Chicle is tapped from the sapodilla tree, which grows in the forests of southern Mexico, Guatemala and Belize. Tappers cut shallow channels in the bark and collect the latex, much as rubber is tapped, and the tree recovers. It has been harvested this way for a very long time.
Mastic is the resin of the mastic tree, a shrub in the pistachio family that is farmed almost entirely on the Greek island of Chios. It has been chewed around the Mediterranean since antiquity, and the word "masticate" comes from it.
Both are plant materials. They are not synthetic polymers, they are not made in a reactor, and when they are eventually discarded they break down the way plant matter does.
How to read a gum label
You do not need a chemistry degree. Three checks:
- Look for the words "gum base". If they appear as a single ingredient with nothing after them, you are looking at the collective term, and the base is almost certainly synthetic.
- Look for named saps. Chicle, mastic, spruce, sapote. If the base is natural, makers tend to say so, because it costs more and they want credit for it.
- Check the sweetener while you are there. Sugar, aspartame, sorbitol and xylitol all appear in different gums, and they are not interchangeable. We have set out what each one actually is separately. If there is a dog in your house, it is worth knowing that xylitol is toxic to dogs, so keep any pack that contains it well out of reach.
Where Perli sits
Perli's base is chicle and mastic, and both are named in full on the pack. There is no "gum base" line on our label, because we would rather you could read what you are chewing. The rest of the ingredient list is on every pack and on each product page, and the story of why we built it this way is on our story page.
Quick answers
Is all chewing gum plastic?
No. Most mass-market gum uses a synthetic polymer base. A small number of brands use tree saps such as chicle and mastic instead. The label tells you which, if you know what to look for.
Is synthetic gum base safe to chew?
Yes. The polymers used are food-grade and permitted by food regulators. The issue is disclosure and what happens to the gum after it is chewed, not safety while chewing.
Is it bad to swallow gum?
Swallowing the occasional piece is not harmful. The old story about it staying in your stomach for seven years is a myth. It passes through undigested like other things the body cannot break down.
Why is gum base allowed to be listed as one ingredient?
Food labelling standards treat gum base as a permitted collective name, similar to the way "spices" or "herbs" can be declared collectively. Manufacturers use it because the exact base recipe is usually a trade secret.
Read next
What is nano-hydroxyapatite? The mineral on the front of every Perli pack, and where it came from.
What actually sweetens sugar-free gum? Xylitol, sorbitol, erythritol and aspartame, explained.